Ever-decreasing network qos requirements for stored video streaming in a mobile wireless interworking environment

ABSTRACT

A method for downloading and displaying a video program using a mobile terminal that includes a first radio access network having a first data transfer rate and a second radio access network having a second data transfer rate faster than the first data transfer rate. The downloaded video program is displayed at a predetermined playback rate. Excess portions of the downloaded video program that result when a rate at which the video program is downloaded exceeds the predetermined playback rate are buffered. A third data transfer rate that is lower than the first transfer rate is calculated in response to the predetermined playback rate, the buffered excess portions and the time duration of the remainder of the video program. The third data transfer rate is negotiated with the first network for downloading the video program when the difference between the first and third data transfer rates exceeds a threshold level.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to networking and, moreparticularly, to a method and a mobile terminal for downloading anddisplaying a video program in an interworking environment comprising afirst radio access network having a first data transfer rate and asecond radio access network having a second data transfer rate.

2. Background of the Invention

In an interworking environment that includes two networks such as, forexample, a Third Generation (3G) cellular network and a Wireless LocalArea Network (WLAN), it is desirable to take advantage of the increasedbandwidth of the WLAN. The coupling of a ubiquitous low speed radioaccess network with a higher speed localized micro-cells provideswidespread coverage with high speeds in certain areas. In that regard, amobile terminal may be able to upgrade to higher data transfer rateswhen the mobile terminal periodically crosses through the higherbandwidth coverage of the WLAN. Renegotiation of the data transfer ratesmay be desirable after downloading portions of the video program at highdata transfer rates. However, a problem may arise from suchrenegotiation because it may not be possible to upgrade the datatransfer rate from the network (Quality of Service (QoS)) due totemporary congestion in the network. In such instances, the QoSnegotiation may not always succeed.

Accordingly, it would be desirable and highly advantageous to have amethod and a mobile terminal capable of taking advantage of increasedbandwidth in an interworking environment, while overcoming theabove-described deficiencies.

SUMMARY OF THE INVENTION

The problems stated above, as well as other related problems of theprior art, are solved by the present invention, which is directed to amethod and mobile terminal for managing the downloading and display of avideo program by the mobile terminal in an interworking environment. Thepresent invention takes advantage of the increased bandwidth provided inhigher bandwidth areas of the interworking environment to reduce thedata transfer rate in lower bandwidth areas. This provides manyattendant advantages to a user including, e.g., reducing the cost to theuser of using the lower bandwidth areas and the probability that therenegotiation of the QoS requirements will succeed.

According to an aspect of the present invention, there is provided amethod for downloading and displaying a video program using a mobileterminal in an interworking environment. The interworking environmentincludes a first radio access network having a first data transfer rateand a second radio access network having a second data transfer ratethat is faster than the first data transfer rate. The video program isdownloaded through the first or second radio access networks atrespective first and second data transfer rates wherein the videoprogram is downloaded at the second data transfer rate when the mobileterminal is in the coverage area of the second radio access network. Thedownloaded video program is displayed at a predetermined playback rate.Excess portions of the downloaded video program that result when a rateat which the video program is downloaded exceeds the predeterminedplayback rate are buffered. A third data transfer rate, which is lowerthan the first data transfer rate, is calculated in response to thepredetermined playback rate, the buffered excess portions and the timeduration of the remainder of the video program. The third data transferrate corresponds to the rate required to maintain the current videoquality in view of the above. The third data transfer rate is negotiatedwith the first access network for downloading the video program when thedifference between the first and third data transfer rates exceeds athreshold level.

According to another aspect of the present invention, there is provideda mobile terminal for downloading and displaying a video program in aninterworking environment. The interworking environment includes a firstradio access network having a first data transfer rate and a secondradio access network having a second data transfer rate that is fasterthan the first data transfer rate. A receiver downloads, through thefirst or second radio access networks, the video program at respectivefirst and second data transfer rates wherein the video program isdownloaded at the second data transfer rate when the mobile terminal isin the coverage area of the second radio access network. A displaydisplays the downloaded video program at a predetermined playback rate.A memory device buffers excess portions of the downloaded video programthat result when a rate at which the video program is downloaded exceedsthe predetermined playback rate. A processor calculates a third datatransfer rate, which is lower than the first data transfer rate, inresponse to the predetermined playback rate, the buffered excessportions and the time duration of the remainder of the video program.The processor controls the negotiation, via a transmitter, of the thirddata transfer rate with the first access network for downloading thevideo program when the difference between the first and third datatransfer rates exceeds a threshold value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a mobile terminal 100 to whichthe present invention may be applied, according to an illustrativeembodiment of the present invention;

FIG. 2 is a block diagram illustrating an interworking environment 200to which the present invention may be applied, according to anillustrative embodiment of the present invention; and

FIG. 3 is a flow chart illustrating the steps for downloading anddisplaying a video program using a mobile terminal in an interworkingenvironment, according to an illustrative embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a method and a mobile terminal fordownloading and displaying a video program in an interworkingenvironment. The present invention takes advantage of the increasedbandwidth provided in higher bandwidth areas of the interworkingenvironment to negotiate a reduced data transfer rate (QoS) in lowerbandwidth areas. Moreover, the present invention provides a methodologyto ensure Quality of Service (QoS) renegotiation in the lower bandwidthareas without degrading video quality. As used herein, the phrase “videoprogram” refers to a program that includes, at the least, video data,and may or may not also include other data such as, for example, audiodata.

It is to be understood that the present invention may be implemented invarious forms of hardware, software, firmware, special purposeprocessors, or a combination thereof. Preferably, the present inventionis implemented as a combination of hardware and software. Moreover, thesoftware is preferably implemented as an application program tangiblyembodied on a program storage device. The application program may beuploaded to, and executed by, a machine comprising any suitablearchitecture. Preferably, the machine is implemented on a computerplatform having hardware such as one or more central processing units(CPU), a random access memory (RAM), and input/output (I/O)interface(s). The computer platform also includes an operating systemand microinstruction code. The various processes and functions describedherein may either be part of the microinstruction code or part of theapplication program (or a combination thereof) that is executed via theoperating system. In addition, various other peripheral devices may beconnected to the computer platform such as an additional data storagedevice and a printing device.

It is to be further understood that, because some of the constituentsystem components and method steps depicted in the accompanying Figuresare preferably implemented in software, the actual connections betweenthe system components (or the process steps) may differ depending uponthe manner in which the present invention is programmed. Given theteachings herein, one of ordinary skill in the related art will be ableto contemplate these and similar implementations or configurations ofthe present invention.

The present invention is directed to an interworking environment. Suchan interworking environment may include, for example, ubiquitous lowspeed first radio access network and a second radio access networkhaving a much higher data transfer speed and lower access cost. Thepresent invention allows users with relatively high mobility to takefull advantage of such an environment in stored video streamingapplications.

Examples of low rate radio access networks to which the presentinvention may be applied (e.g., radio A above) include, but are notlimited to, fixed or mobile wireless wide area networks such as thirdgeneration (3G), second generation plus (2.5G), second generation (2G),and first generation (1G) cellular networks, and so forth. Examples ofhigh rate radio access networks to which the present invention may beapplied (e.g., radio B above) include, but are not limited to, WirelessLocal Area Networks (WLANs) and so forth. The WLANs may be, for example,those compliant with IEEE 802.11 or Hiperlan 2.

For ease of presentation, the following description of the presentinvention shall generally employ a 3G cellular network as the firstradio access network and a WLAN as the second radio access network.However, it is to be appreciated that the present invention is notlimited to the preceding communication technologies and network typesand, thus, other communication technologies and network types may alsobe readily employed by the present invention while maintaining thespirit and scope of the present invention. Moreover, it is to beappreciated that the present invention may be applied to an interworkingbetween more than two networks while maintaining the spirit and scope ofthe present invention. Further, it is to be appreciated that the presentinvention may be applied to all or a subset of the networks that arepart of an interworking while maintaining the spirit and scope of thepresent invention.

According to an illustrative embodiment of the present invention, amobile terminal downloads the video program at the first data transferrate from the first radio access network, and at the second datatransfer rate as the mobile terminal crosses through coverage areas ofthe second radio access network. The downloaded program data isprocessed at a predetermined playback rate and displayed on displaydevice. Due to the higher data transfer rate in the second radio accessnetwork areas, excess program data may result. The excess program datathat result when the download rate exceeds the playback rate is bufferedinto a memory device. A third data transfer rate can be calculated inresponse to the predetermined playback rate, the buffered excessportions and the time duration of the remainder of the video program.This third data transfer rate corresponds to the data transfer raterequired in view of the above factors. When the difference between thefirst and third data transfer rates is sufficient, i.e., exceeds athreshold level, the mobile terminal renegotiates the third datatransfer rate with the first radio access network for downloading thevideo program, wherein the third data transfer rate is lower than thefirst data transfer rate. This ensures that the video quality is notdegraded even if the data transfer rate falls to the third data transferrate for the remainder of the program playback time.

FIG. 1 is a block diagram illustrating a mobile terminal 100 to whichthe present invention may be applied, according to an illustrativeembodiment of the present invention. The mobile terminal 100 includes areceiver 110, a transmitter 120, a display 130, a memory 140, and aprocessor 150, all interconnected by a bus 179. The receiver 110 andtransmitter 120 are configured to receive/transmit data from/to eitherone of the two radio access networks. The mobile terminal may be, but isnot limited to, a cellular phone, a Personal Digital Assistant (PDA), alaptop computer, and so forth. The arrangement and operation of suchelements in those devices are well known to those skilled in the art.

FIG. 2 is a block diagram illustrating an interworking environment 200to which the present invention may be applied, according to anillustrative embodiment of the present invention. The interworkingenvironment 200 includes a first radio access network 210, which in theillustrative embodiment is a 3G network, and second radio access networkareas 220, which in the illustrative embodiment are WLANs, dispersedthere through. A mobile terminal 100 moves through coverage areas of thefirst and second radio access networks, possibly including areas of dualcoverage. A server 270, reachable from both the first radio accessnetwork and the second radio access network, provides a source fromwhich a video program can be downloaded to the mobile terminal 100.

It is to be appreciated that the present invention is not limited toprecisely the interworking environment shown and described with respectto FIG. 2 and, thus, other interworking environments may also beemployed while maintaining the spirit and scope of the presentinvention.

Once in a WLAN cell, a Mobile Terminal (MT) starts downloading the videoprogram to local storage at the higher WLAN data transfer rate. Giventhe discrepancy between the downloading rate and the playback rate,after some time has elapsed from the start of downloading, the MT willhave a certain amount of buffered video. One way to make use of thebuffered amount is to decrease the QoS requirement (data transfer rate)once the MT moves into 3G coverage, thus decreasing the cost of 3Gaccess. With this option, it is desirable to ensure that the videoquality will not be degraded throughout the rest of the video session.However, it cannot be assumed that once the QoS requirement on the 3Gnetwork is decreased, the QoS requirement can be upgraded at some latertime. The problem is that the network may not be able to honor a requestto increase the rate due to, for example, temporary congestion in thenetwork. Thus, the present invention provides a method thatadvantageously decreases the data transfer rate while ensuring that thesame quality is maintained for the remainder of the video session.

For illustrative purposes, the following notations are employed herein:

Buffered amount: B_(t)

Data transfer rate in the 3G coverage area: R_(g),

Playback rate: R_(p)

Time duration for the rest of the video: T

Moreover, the following constraint is employed:(R _(p) −R _(g))*T←B _(t)The MT calculates the new required rate based on the above constraint:R _(g) ′=R _(p) −B _(t) /TWhen the MT decides that there's enough rate difference between the newrequired rate and the first data transfer rate to renegotiate the ratewith the network, the mobile terminal will renegotiate with the 3Gnetwork using this new rate. The sufficiency of the rate difference canbe determined based on a predetermined threshold level, or may beadjusted for the program as desired. It is apparent that the new rateR_(g)′ is always smaller than the old rate R_(g). We can see this moreclearly as follows. If we didn't enter the WLAN cell, we would have thefollowing equation:R _(g) =R _(p) −B _(old) /Twhere B_(old) is the buffered amount if we didn't enter the WLAN cell.It is apparent that B_(t) is bigger than B_(old), thus R_(g)′<R_(g).Thus the renegotiation will always succeed.

FIG. 3 is a flow chart illustrating the steps downloading and displayinga video program in an interworking environment that includes a firstradio access network and a second radio access network, according to anillustrative embodiment of the present invention. In the illustrativeembodiment of the FIG. 3, the first radio access network has a firstdata transfer rate, which may be negotiated between a mobile terminaland the first radio access network, and the second radio access networkhas a second data transfer rate that is faster than the first datatransfer rate.

It is determined whether the mobile terminal is in a coverage area ofthe second radio access network (step 305). If so, the mobile terminalattaches to the second radio access network, if not already done, anddownloads the video program at the second (faster) data transfer rate(step 315). As the data transfer rate is higher than the rate at whichthe data is processed and displayed, an excess develops, and the excessdata is buffered, or stored in a memory device in step 325.

If the mobile terminal is not in a coverage area of the second radioaccess, the mobile terminal determines whether it is in a coverage areaof the first radio access network (step 310). If not, the process stops.If so, the mobile terminal downloads the video program at a datatransfer rate negotiated with the first radio access network (step 320).

The downloaded video program is displayed on a display device at apredetermined playback rate (step 330). As the downloaded video programis displayed, the mobile terminal calculates, either periodically orcontinuously, a new data rate in response to the predetermined playbackrate, the buffered excess portions and the time duration of theremainder of the video program (335). The new data rate reflects therequired data rate for maintaining the quality of the video display inview of the buffered excess portions of the video program and theremaining time of the video program.

The mobile terminal then determines whether the difference between thenew data rate determined in step 335 and the currently negotiated datatransfer rate with the first radio access network exceeds a thresholdlevel. The threshold level may be a set predetermined level or adjustedas desired (step 340). The threshold value may be equal to, for example,the time duration of the remainder of the video program to be playedback multiplied by the difference between the predetermined playbackrate and the first data transfer rate. Using the nomenclature definedabove, the threshold as previously described may be represented asfollows:threshold=T*(Rp−Rg)

If difference does not exceeds the threshold level, the process returnsto step 305 and continues downloading the video program as desired. Ifthe difference exceeds the threshold level, the process continues tostep 345 to renegotiate a new data transfer rate with the first radioaccess network, which is lower than the previously negotiated datatransfer rate. The process then returns to step 305 to continuedownloading the video program as desired.

Given the possibility that there may be some overlapping coveragebetween the first radio access network and the second radio accessnetwork, it is to be appreciated that the negotiation of the new datatransfer rate with the first radio access network by the mobile terminalmay be performed at any time that such negotiation is possible includingwaiting (or not) for the mobile terminal to be entirely outside thecoverage area of the second radio access network. That is, given theteachings of the present invention provided herein, one of ordinaryskill in the related art will contemplate these and various other timeinstances for when the negotiation can take place in relation to thepositioning of the mobile terminal with respect to the coverage areas ofthe first and second radio access networks.

It is also to be appreciated that the mobile terminal may or may nothave been in the coverage area of the first radio access network anddownloading the video program in that area (at the first (slower) datatransfer rate) prior to entering the coverage area of the second radioaccess network as determined at step 305. That is, the present inventiondoes not require any particular or pre-specified sequence of movementsby the mobile terminal through the various networks to obtain thebenefits of the present invention. All that is necessary is for bufferedexcess portions of the downloaded video program to be accumulated in thebuffer such that a sufficient rate difference between the first datatransfer rate and a new data transfer rate can be generated.

Advantageously, the present invention decreases the network QoSrequirement (and, thus, cost) as the direct benefit of “occasionallycrossing” WLAN cells. Moreover, the present invention advantageouslyprovides a methodology such that the QoS requirement renegotiation withthe network will always succeed. Further, the present invention does notresult in any degradation of quality throughout the video session.

Although the illustrative embodiments have been described herein withreference to the accompanying drawings, it is to be understood that thepresent invention is not limited to those precise embodiments, and thatvarious other changes and modifications may be affected therein by oneof ordinary skill in the related art without departing from the scope orspirit of the invention. For example, although the present embodimentsare described with reference to video programs, it is clear that thepresent invention is applicable to audio programs, and other multimediaprograms that may be downloaded through radio access networks. All suchchanges and modifications are intended to be included within the scopeof the invention as defined by the appended claims.

1. A method for downloading and displaying a video program using amobile terminal in an interworking environment that includes a firstradio access network having a first data transfer rate and a secondradio access network having a second data transfer rate that is fasterthan the first data transfer rate, the method comprising the steps of:downloading, through the first or second radio access networks, thevideo program at respective first and second data transfer rates, thevideo program being downloaded at the second data transfer rate when themobile terminal is in the coverage area of the second radio accessnetwork; displaying the downloaded video program at a predeterminedplayback rate; buffering excess portions of the downloaded video programthat result when a rate at which the video program is downloaded exceedsthe predetermined playback rate; calculating a third data transfer rate,which is lower than the first data transfer rate, in response to thepredetermined playback rate, the buffered excess portions and the timeduration of the remainder of the video program; and negotiating, withthe first access network, the third data transfer rate for downloadingthe video program, when the difference between the first and third datatransfer rates exceeds a threshold level.
 2. The method of claim 1,wherein the third data transfer rate is equal toRp−B_(t)/T where Rp is the predetermined playback rate, B_(t) is anamount of the buffered excess portions of the downloaded video program,and T is a time duration of the remainder of the video program to beplayed back.
 3. The method of claim 1, further comprising the step ofcontinuing to download the video program from the first radio accessnetwork using the third data transfer rate when the mobile terminalleaves the coverage area of the second radio access network and iswithin the coverage area of the first radio access network.
 4. Themethod of claim 1, wherein the negotiating step is performed when themobile terminal is within the coverage area of the second radio accessnetwork.
 5. The method of claim 1, wherein the negotiating step isperformed after the mobile terminal leaves the coverage area of thesecond radio access network.
 6. The method of claim 1, wherein the firstradio access network is a 3G cellular network.
 7. The method of claim 1,wherein the second radio access network is a Wireless Local Area Network(WLAN).
 8. A mobile terminal for downloading and displaying a videoprogram in an interworking environment that includes a first radioaccess network having a first data transfer rate and a second radioaccess network having a second data transfer rate that is faster thanthe first data transfer rate, the mobile terminal comprising: a receiverfor downloading, through the first or second radio access networks, thevideo program at respective first and second data transfer rates, thevideo program being downloaded at the second data transfer rate when themobile terminal is in the coverage area of the second radio accessnetwork; a transmitter for transmitting data to the first or secondradio access networks; a display for displaying the downloaded videoprogram at a predetermined playback rate; a memory device for bufferingexcess portions of the downloaded video program that result when a rateat which the video program is downloaded exceeds the predeterminedplayback rate; and a processor for calculating a third data transferrate, which is lower than the first data transfer rate, in response tothe predetermined playback rate, the buffered excess portions and thetime duration of the remainder of the video program, the processorcontrolling the negotiation of the third data transfer rate with thefirst access network for downloading the video program when thedifference between the first and third data transfer rates exceeds athreshold value.
 9. The mobile terminal of claim 10, wherein the thirddata transfer rate is equal toRp−B_(t)/T where Rp is the predetermined playback rate, B_(t) is anamount of the buffered excess portions of the downloaded video program,and T is a time duration of the remainder of the video program to beplayed back.
 10. The mobile terminal of claim 10, wherein the receivercontinues to download the video program from the first radio accessnetwork using the third data transfer rate when the mobile terminalleaves the coverage area of the second radio access network and iswithin the coverage area of the first radio access network.
 11. Themobile terminal of claim 10, wherein the third data transfer rate isnegotiated when the mobile terminal is within the coverage area of thesecond radio access network.
 12. The mobile terminal of claim 10,wherein the third data transfer rate is negotiated after the mobileterminal has left the coverage area of the second radio access network.13. The mobile terminal of claim 10, wherein the first radio accessnetwork is a 3G cellular network.
 14. The mobile terminal of claim 10,wherein the second radio access network is a Wireless Local Area Network(WLAN).